Permanent magnet motors are widely used, especially in automobiles. A permanent magnet motor typically includes a stator having permanent magnets and a wound rotor rotatably mounted to the stator. The stator includes a housing accommodating the magnets. The magnets are bonded to the housing by adhesive. During the bonding process, adhesive is applied on the outer surface of the magnets. Then the magnets are placed on a holder, and then the magnets are pressed to the inner surface of the housing by the holder, such that the magnets are bonded to the housing by the adhesive.
As the magnets with adhesive thereon should be positioned on the holder manually, two circumferential ends of the outer surface of the magnet should be free of adhesive for operator grabbing. As a result, circumferential ends of the magnets are not bonded to the housing due to the absence of the adhesive, and thus gaps are formed between the inner surface of the housing and the outer surface of the magnet at the circumferential ends of the magnets. When the motor operates, high frequency resonance will occur between the housing and the magnets where the gaps exit, due to the interaction between the magnets and the wound rotor. Such resonance results in undesirable noise.